At least I concluded so by the difference of their tones and gestures.

For myself, I had looked carefully in the direction indicated without seeing anything.

The sky and water were lost in the clear line of the horizon.
However, Captain Nemo walked from one end of the platform to the other, without looking at me, perhaps without seeing me.

His step was firm, but less regular than usual.

He stopped sometimes, crossed his arms, and observed the sea.